Polkadot is a multi-chain platform that enables interoperability between different blockchains. It provides a secure environment for developers to build decentralized applications and allows them to seamlessly connect to other blockchains. Polkadot uses a unique sharding mechanism to process transactions faster and more efficiently while maintaining security. Its native token, DOT, is used for governance and transaction fees. Polkadot aims to become the foundation of a decentralized web.